Abstract

Background

Immune suppression may be a critical effect associated with exposure to perfluorinated
compounds (PFCs), as indicated by recent data on vaccine antibody responses in children.
Therefore, this information may be crucial when deciding on exposure limits.

Methods

Results obtained from follow-up of a Faroese birth cohort were used. Serum-PFC concentrations
were measured at age 5 years, and serum antibody concentrations against tetanus and
diphtheria toxoids were obtained at age 7 years. Benchmark dose results were calculated
in terms of serum concentrations for 431 children with complete data using linear
and logarithmic curves, and sensitivity analyses were included to explore the impact
of the low-dose curve shape.

Results

Under different linear assumptions regarding dose-dependence of the effects, benchmark
dose levels were about 1.3 ng/mL serum for perfluorooctane sulfonic acid and 0.3 ng/mL
serum for perfluorooctanoic acid at a benchmark response of 5%. These results are
below average serum concentrations reported in recent population studies. Even lower
results were obtained using logarithmic dose–response curves. Assumption of no effect
below the lowest observed dose resulted in higher benchmark dose results, as did a
benchmark response of 10%.

Conclusions

The benchmark dose results obtained are in accordance with recent data on toxicity
in experimental models. When the results are converted to approximate exposure limits
for drinking water, current limits appear to be several hundred fold too high. Current
drinking water limits therefore need to be reconsidered.